Question

Figure shows a block-and-tackle system of pulleys used to lift a load. 

1. How many strands of tackle are supporting the load?
2. Draw arrows to represent tension in each strand.
3. What is the mechanical advantage of the system?
4. When the load is pulled up by a distance of 1 m, how far does the effort end move?

Answer 1

(a) 4 stands marked 1, 2, 3, and 4 support the load L.

(b) The strands tension in the T direction is shown.

(c) M.A. = L = 4T and E = T

M.A. = `L/E`

= `(4T)/T = 4`

(d) As load is pulled up by 1 m

d_L = 1m = d

Distance moved by effort = d_E = nd

V.R. = `d_E/d_L`

= `(nd)/d`

= n = 4m